Solid state transducer (SST) devices include light-emitting diodes (“LEDs”), organic light emitting diodes (“OLEDs”), and polymer light-emitting diodes (“PLEDs”). The energy efficiency and small size of solid state transducer devices has led to the proliferation of these devices in a multitude of products. Televisions, computer monitors, mobile phones, digital cameras, and other electronic devices utilize LEDs for image generation, object illumination (e.g., camera flashes) and/or backlighting. LEDs are also used for signage, indoor and outdoor lighting, traffic lights, and other types of illumination. Improved fabrication techniques for these semiconductor devices have both lowered device cost and increased device efficiency.
Solid state transducer devices and other semiconductor devices are often fabricated using epitaxial growth techniques. Typically, an epitaxial film is grown on a wafer or a substrate in a controlled process that includes elevated temperatures. In a heteroepitaxy process, the substrate and the epitaxial film are composed of different materials having dissimilar coefficients of thermal expansion (CTE). Under high temperature manufacturing conditions, the distinct CTEs of the differing materials can cause the substrate and the epitaxial film to expand or contract at significantly differing rates, which can result in stresses that bow or warp the substrate either during or after the growth of the epitaxial film. Bowing or warping the substrate during the growth of the epitaxial film can reduce the uniformity of the film and thereby reduce the performance of the semiconductor device manufactured with the film. Furthermore, bowed or warped wafers can complicate further processing of the semiconductor device. For example, semiconductor devices constructed on substrates using epitaxial growth techniques are often singulated in a later processing step to produce a multitude of semiconductor devices from a single assembly. Warping, delamination and/or other defects can lead to misalignments during the singulation process which in turn can cause defects in the semiconductor devices.
One conventional approach to reducing the negative effects of dissimilar CTEs is to increase the substrate thickness. However, this does not entirely eliminate the problem because the stresses can still lead to delamination of the film from the substrate, or smaller, but still consequential bowing or warping. In addition to the above-mentioned problems with the fabrication of semiconductor devices, and the resulting defects, existing substrates are often sacrificed, wasted or otherwise destroyed in the manufacturing process, thereby increasing the cost of the semiconductor devices. Accordingly, there is a need for a solid state transducer device and a method of fabrication that can avoid or mitigate these limitations.